The present invention relates to an improvement of an electrostatic induction conversion device for converting between electric energy and kinetic energy.
Conventionally, a power generator, a microphone or the like using an electret in which an electric charge is injected in an insulating material has been proposed. In an apparatus using the electret as stated above, it is known that conversion efficiency between electric energy and kinetic energy is high. For example, JP-A-58-6118 and Japanese Patent No. 3545982 disclose examples of power generators using electrets.
In the above conventional technique, as a material of the electret, fluorinated resin such as PTFE (polytetrafluoroethylene) or Teflon (registered trademark) AF, silicon oxide or the like is used. However, any of the materials have problems in workability into a fine shape or in that the thickness of the electret is increased in order to raise the output of power generation. For example, with respect to polytetrafluoroethylene, although the thickness of the electret can be made large, there has been a problem that it is available only in the form of a plate member, and its fine processing properties are low. Besides, with respect to Teflon (registered trademark) AF, although spin coating can be performed, since plasma etching is difficult, there has still been a problem that its fine processing properties are not very high. Besides, with respect to silicon oxide, although fine processing can be performed, there has been a problem that the thickness of the electret can not be made large.
Further, in the case where the above material is used, there has also been a problem that the electric charge injected in the electret is lost by moisture in the air, and the electret is deteriorated.